archinstall 4.3's Installer.__init__ types target as Path and uses it
directly (self.target / 'boot', etc.). Passing str(mountpoint) makes
self.target a str, so every internal path operation raises
'unsupported operand type(s) for /: str and str' — most visibly during
set_mirrors, which constructs target / MIRRORLIST.relative_to_root().
Drop the str() cast; pass the Path through as-is.
Ryan Hughes
34c0a14766